CalPundit asks today whether there is such a thing as athletic ability. He lists a number of factors that contribute to athletic ability, to which I'd add body shape/size, stamina, and a set of mental attributes like agressiveness and competitiveness.

Athletic ability is, by definition, the ability to perform athletic feats. A brief consideration will show that ability in one athletic feat does not necessarily translate to ability at another athletic feat. You can be a great cross-country runner but a terrible football player, and vice versa. Different athletic feats require different muscles, different body types (think sumo wrestler vs jockey), and so forth. This applies within sports as well as between them -- it takes different qualities to be able to hit home runs vs to be able to pitch a no-hitter. Yet this does not mean that everyone is equally athletically talented, though. There are complementarities among athletic training and genetic proclivities for various sports.

The question that arises, then, is whether we can aggregate abilities at different athletic feats into a single scale of ability, and (crucially) whether that aggregation is useful for anything. Aggregating abilities would require us to be able to put ability within each athletic task on a common scale. Since sports commentators argue for ages about which players are better than others, I have doubts of our ability to do that. But let's say we could, through a series of laboratory tests, establish a person's ability to throw, and to block pucks, and to run, and so forth. We'd still face the problem of how to combine them. Is each element equally valuable? Or should they be weighted somehow? And on what basis would you assign weights -- maybe the prevalence of each activity within the sports that are currently played around the world? It seems an impossible task.

Thus, athletic ability is not a universally operational concept -- it's not a thing, but rather a vague and informal aggregate of things. However, it becomes more operational as the context and goals become more specific -- because you're trying to combine fewer things. It's easier to say how good a runner John is than to say how good an athlete he is.